1. Field of the Invention
The present invention relates to methods for the restoration of a decayed portion of an anterior tooth or re-restoration of a previously filled anterior tooth, and to dental matrices and composite resin dispensers that may be used in the methods for the restoration of a decayed portion of an anterior tooth.
2. Description of the Related Art
Dental cavities that have spread to the dentin or have undergone cavitation are typically treated by removing the decayed portion of the tooth and thereafter filling the missing tooth structure with a restorative material such as silver (amalgam), white (resin), porcelain, or gold. Cavities that are located adjacent to neighboring teeth are called interproximal cavities.
When treating interproximal cavities, the dentist first removes the decayed portion of the side of the tooth. In order to properly deposit the restorative material on the side of the tooth without undesired leaking of the restorative material beyond the side of the tooth, the dentist places a dental matrix around at least a portion of the tooth. The dental matrix may be a metallic or plastic strip, and when the matrix is placed around at least a portion of the tooth, the matrix acts as a form for the desired shape of the restored tooth. Various dental matrix bands are shown in U.S. Pat. Nos. 6,712,608, 6,619,956, 6,350,122, 6,142,778, 6,079,978, 5,975,906, 5,807,101, 5,730,592, 5,622,496, 5,501,595, 5,460,525, 5,425,635, 5,114,341, 4,997,367, 4,781,583, 4,718,849, 4,704,087, 4,601,662, 4,553,937, 4,536,155, 4,523,909, 4,024,643, 3,842,505, 3,108,377, and 2,611,182, and U.S. Patent Application Publication Nos. 2006/0019217 and 2005/0089814. The disadvantages of these known matrix bands is that they are not truly anatomic and therefore, they must be conformed to the tooth by pressure or other means. As a result, these matrixes are inefficient in that more dentist time is needed to complete the restoration, and the final result may be a non-anatomic restoration.
In the past a flat clear (e.g., Mylar™ plastic) strip was placed after the cavity was prepared and often adapted with an interdental wedge or elastic spacer. There have been problems with previous techniques. The problems with traditional clear Mylar™ plastic strips are that they are flat and require wedging, and do not conform to the tooth.
After the cavity was prepared, the composite was placed onto or partially injected onto the tooth. The composite was then packed into the cavity preparation. Finally, the flat clear or metallic matrix was engaged with fingers or instruments to wrap around the tooth, and then simultaneously a light cure unit was placed in proximity to the tooth to initiate photo-curing or polymerization of the composite. Holding all four ends of the strips while simultaneously light-curing is always a challenge. The problems of the traditional technique included flat interdental shapes that are an esthetic and health liability. In particular, the “dark triangle” that often occurs is caused by insufficient buttressing of the gingival triangle which is seeking two approximating rounded interdental tooth profiles.
It is believed that no attempt has been made to present for a sectional curved and or anatomically shaped nor tooth specific matrix nor surface specific matrix for anterior teeth.
The anterior tooth has a complex shapes with multiple curvatures. It is asymmetrical from front side to back side (facial to lingual) and from right to left (mesial to distal). Sectional clear flat matrix strips for anterior teeth have been available. These fillings today are performed nearly universally with tooth colored filling materials (composite resin) and require a medium to contain the filling material inside the cavity preparation. These matrix strips are translucent, and typically made from Mylar™ plastic material that is thin and pliable. It is believed that to date there are no sectional matrices available for anterior teeth other than a flat Mylar™ plastic strip.
It is believed that the only anatomic (non-flat) shaping device for anterior teeth currently sold is a strip crown that is formed from a stiff material such as polycarbonate. They are used for temporization or building up of a severely broken down tooth. Composite material is placed inside of the strip crown, cured with light or chemical polymerization, and then the polycarbonate can be stripped away (in the case of a long term “build-up”, such as is done until permanent dentistry is undertaken) leaving a tooth built up with composite. The relatively crude shape of the buildup is then eventually prepared (ground down) to the peg shape typically performed in preparation for a veneer-crown. A crown is then fabricated in a laboratory or with CAD CAM and then the tooth receives a crown to permanently cover the “build-up”. Alternatively the strip crown can be left in place as a temporary veneer crown. The thickness and stiffness of the “strip crown” disallows its use for interproximal fillings. Hence the use of flat Mylar™ plastic strips is the norm today.
Some problems with current flat plastic matrix strips for anterior teeth include: (1) the flat plastic matrix strips are flat (not anatomic), requiring crimping; (2) the flat plastic matrix strips require stabilizing with wedges or other devices; (3) the flat plastic matrix strips require further stabilizing with the operator's fingers or the dental assistant's fingers, and back to back fillings (two neighboring teeth with interproximal caries or failing fillings) present extreme challenges to manipulate four matrix ends simultaneously; (4) the flat plastic matrix strips require that the strip be “wrapped” to approximate the tooth after placement of filling material (such as a composite, glass ionomer, composite/glass ionomer mix) and prior to polymerization or light curing of the material; (5) time and energy is usually expended to remove excess and areas of bulky, non anatomic regions of the composite filling material because of the residual contour created by the flat, non anatomic clear strip; (6) the above mentioned finishing can lead to gum trauma and can lead to iatrogenic gouging of tooth surface and tooth surfaces of neighboring teeth; (7) the above mentioned finishing disturbs the smooth and highly cured surface left by the plastic strip and while this disturbed surface can be polished, it is virtually impossible to return to the original smoothness and these surfaces are manifested clinically as a matte finish, rough finish, or jagged finish and these three imperfect finish types collect bacteria more readily, are more prone to discoloration and predispose the tooth to decay and predispose the periodontal attachment (gum and bone) to deterioration from the destructive nature of periodontal diseases; (8) the flat matrix strip combined with a wedge often results in a flat contoured filling that has an unsightly gapping (dark triangle) between the teeth at the gum attachment area such that food and bacterial accumulation are also more common in these gaps; and (9) the pre curved sectional matrix bands for posterior teeth are too short to be used easily on anterior teeth as matrix bands for posterior teeth range from 4.5 millimeters to 6.5 millimeters in height, and the needs of anterior teeth range approximately from 8 millimeters to 13 millimeters in height.
Thus, there is a need for improved dental matrices, particularly dental matrices intended for anterior teeth.
As detailed above, removed tooth structure is often filled with a composite restorative material such as white filled resin. While flowable composites have been available for quite some time and can provide for ease of filling intricate dental cavity preparations, the ability of paste composite material to flow and adapt to the intricacies of a dental cavity preparation can be compromised if the viscosity of the paste composite is too high. Thus, paste composite can pose difficulties in advanced injection molded cavity preparation and filling techniques such as that described in U.S. Patent Application Publication No. 2008/0064012. However, in comparison to flowable composite, paste composite has been shown to be superior in that paste composite has less polymerization shrinkage, less wearing over years of mastication, improved polishability, and improved strength.
It has been proposed that dental materials can be heated before or during extrusion to reduce viscosity so that the restorative material expressed from a dental capsule can better adapt to the walls of a cavity preparation and to the intricacies of the cavity preparation. See, for example, U.S. Pat. Nos. 6,312,254, 6,320,162, 6,616,448 and 7,097,452. Although some benefits of heated composite materials have been reported in these patents, adoption of this technique has been very limited. Composite manufacturers have not adopted significant changes to their delivery systems to capitalize on the concept and benefits of heated composite. For example, the tip orifice size of typical current paste composite syringes (examples include Filtek Supreme PLUS™ available from 3M, St. Paul, Minn., USA) is significantly larger than the orifice tip size of the flowable type composites. In the case of this example product from 3M, the paste syringe orifice is approximately 2.5 millimeters in diameter, while the 3M flowable composite tip size is less than 1 millimeter. See also, U.S. Pat. No. 7,001,932 in which a composite is filled in a syringe having an internal tip diameter of 2 millimeters.
Accordingly, it can be appreciated that in the field of composite dental restorative materials, there is a need for improved composite dispensers and methods such that paste composite can have its handling characteristics improved to handle more like the less robust but easier to apply flowable composites.